xfs: rename xfs_ilock_map_shared

Make it clear that we're only locking against the extent map on the data
fork.  Also clean the function up a little bit.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

diff --cc fs/xfs/xfs_aops.c
Simple merge

diff --cc fs/xfs/xfs_bmap_util.c
Simple merge

diff --cc fs/xfs/xfs_file.c
Simple merge

diff --cc fs/xfs/xfs_inode.c
Simple merge

diff --cc fs/xfs/xfs_inode.h
Simple merge